void calc_show_los();

class los_def
{
    env_show_grid show;
    coord_def const * center;
    opacity_func const * opc;
    const bounds_func * bds;
public:
    los_def();
    los_def(const coord_def& c, const opacity_func &o = opc_default,
                                const bounds_func &b = bds_default);
    void init(const coord_def& c, const opacity_func &o = opc_default,
                                  const bounds_func &b = bds_default);
    void update();
    void set_center(const coord_def& center);
    bool see_cell(const coord_def& p) const;
};

void calc_show_los();

}
// class los
// TODO: lazy update?
los_def::los_def() {}
los_def::los_def(const coord_def& c, const opacity_func &o,
                             const bounds_func &b)
{
    init(c, o, b);

void los_def::init(const coord_def& c, const opacity_func &o,
                                   const bounds_func &b)
{
    center = &c;
    opc = &o;
    bds = &b;
    update();
}
void los_def::update()
{
    losight(show, *center, *opc, *bds);
}
void los_def::set_center(const coord_def& c)
{
    center = &c;
    update();
}
bool los_def::see_cell(const coord_def& p) const
{
    return (::see_cell(show, *center, p));
}